Oven-thermometer.



C. D. BOLIN.

OVEN THERMOMETER.

APPLICATION FILED FEB. I8, 1916.

Patented May 8, 1917.

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Specification of Letters Patent.

. Patented May 8, 1917.

Application filed February 18, 1916. 1 Serial No. 79,087.

To all whom it may concern: Be it known that I, GrrAnLns D. BoLIN,

a citizen of the United States, and a resident of the city of St. Louisand State of Missouri, have invented a new and useful Improvement inOven-Thermometers, of which the following is a specification.

This invention is an improvement in thermometers of the type shown in myapplication for patent filed July 6, 1915, Serial No. 38,080, wherein abi-metallic spring forms the heat sensitive element. The inventionrelates particularly to the construction and arrangement of thethermometer case, spring and indicating mechanism for responding quicklyto the changes in temperature and for protecting the parts from injuryand abuse.

The object ofthe invention is to reduce the number of parts, and tocheapen the cost of manufacture, of such thermometers by simplifying theconstruction of the case and the assembling therein of the operatingparts. Further details of the inventionappear in the followingdescription of the oven thermometer illustrated in the accompanyingdrawings, and what the invention consists in is more particularlydefined in the appended claims.

In the drawings, in which like parts are designated by the samereference characters in the several views.

Figure 1 is a front view of an oven ther mometer made in accordance withthis invention, the front cover being partly broken away;

Fig. 2 is'a front view of the same with the front glass and its retainerremoved, the front of the case partly broken away, and the index pointerbroken ofl to show the parts within the inner chamber of the case;

Fig. 3 is a vertical cross-section of the same on the line 3-3 in Fig.1;

Fig. 4 is a perspectiveview of a portion of the case; and

Fig. 5 is a perspective view of the back assembledwith the heatsensitive spring and index-pointer pivot, ready for pressing into thecase.

Referring to the drawings, the improved device comprises a shallow cupshape cylindrical casing 11, arranged with its open side at the back andhaving an opening 12 through its edge at the front for the indexpointer. This opening extends laterally around the periphery of the caseas shown in Fig. i to permit the index pointer to be inserted throughit. The open side of the casing 11 is closed by a cup shape back 13which forms a support for the heat sensitive spring and indicatingmechanism. The casing 11 has a back flange projecting out around itsedge with two diametrically opposed ears or lugs 14 provided with holes15 through which may be passed bolts or screws for securing the deviceto the door of an oven. The front face of the casing 11 pro ects throughthe oven door, and a face or dial 16 is enameled directly upon it. Overthe dial is a glass 17, held by an outer casing ring'18 which surroundsthe casing 11 and which has'an inturned lip or flange inclosing theglass. within the casing ring 18 between the glass and the dialholds'the glass spaced away from the dial and in contact with theflange, as shown in Fig. 3. The separator ring is concave incross-section, and itslower edge conceals the irregular edge of thedial.

The heat sensitive spring 20 is flat, and is riveted at one end to theedge of a post 23 which is secured to the back member 18 of the casing.The other end of the spring 20 carries a finger or pin 24 which isfixedly secured to the spring on one side and which projects outwardlybeyond the edge of the spring toward the dial to engage the slot in thearm 25 on the inner end of the index pointer.

The heat sensitive spring is composed of two leaves 21, 22, securedtogether flatwise,

A separator ring 19v these leaves being made of metals having diflerentcoefficients of expansion, such as nickel, steel and brass. The effectof changes in temperature is to bend or how the spring sidewise, therebycausing the pin to swing the slotted arm 25 and deflect the indexpointer. a

The dial 16 is marked with a scale 27 reading from about 100 to about500 degrees Fahrenheit, and the index pointer has a hand 26 which isarranged to swing in front of the dial over said scale. The indexpointer is pivoted on the outer end of a pivot post 28 which is rivetedat the inner end to the back member 13 of the thermometer case. Thepivoted end of the index pointer has a strap portion 29 which liesalongside of the post and extends through the case, forming an integralconnection between the hand 26 and the inner slotted arm 25. The hand26, connecting portion 29 and inner slotted arm 25 of the index pointerare all made in one piece by stamping them from sheet metal, and arethen bent into the form shown in Fig. 8. In order to assemble the devicethe spring 20 and pivot post 28 are assembled in the back member 13 ofthe casing and are securely riveted thereto, and the back memberispressed into place in the thermometercasing. The pivot post projectsthrough the opening 12 in the front of the casing and the index pointeris slipped over it from the front side, the hand pointing away from thethermometer so that the arm 25 passes through the opening 12. The handis then turned around until it is over the scale on the dial, therebyswinging the arm through the slot 12 into the casing over the spring andcausing the slot in the arm 25 to line up with the pin 24 on the spring.The index pointer is then dropped into place on the pivot pin and theend of the pivot pin is spun or riveted over to secure the parts inposition. The connecting portion 29 of the index pointer can be twistedslightly when the parts are assembled in order to adjust the relativeposition of the hand and inner arm to correspond to any slightirregularities in the setting and shape of the spring. By this means thehand can be adjusted to stand at the proper point on the scale for theparticular temperature at which the instrument is adjusted.

I It is evident that a device made as above described has comparativelyfew parts, which parts are simple in construction and easy to assemble.The heat sensitive spring is straight at ordinary room temperature, andconsequently requires no bending or other adjustment, the relativepositions of the slotted arm and point-er being adjustable to suit'small variations in the setting of the spring. There are only two movingparts, which reduces the lost motion and backlash of the connections andpivots to a minimum, and hence increases the accuracy and life of theinstrument. The back is supported and protected by the case, and is madevery thin so as to readily transmit heat from the oven. to the interiorof the casing. Furthermore, the casing being com pletely closed theparts cannot be tampered with and are protected from injury. Also, nodirt, grease or smoke from the oven can get into the casing to gum up orcorrode the moving parts, and therefore the device will not becomesluggish or inaccurate in the course of a comparatively short time.Excepting the spring the index pointer is the only moving part, and thiscan be made of very light metal so as to be quickly responsive to thetendency of the spring to bend with changes in temperature.

The invention is not limited to the precise forms and arrangement of theparts shown and described.

I claim the following as my invention:

1. A thermometer comprising a case, having a solid front wall and anopen side at the back, a dial on the front wall of said case, a backclosing the open side of said case and fixed thereto, "a heat sensitivespring and a pivot post secured to said back,

said pivot post projecting through the front wall of said case, apointer rotatable on the end of said pivot post, said pointer having anarm within said case pivoted on said post and adapted for cooperationwith said spring.

2. A thermometer comprising a cupped case inclosing a heat sensitivespring, the front wall of said case having an enamel dial thereon, aretainer ringsu-rrounding said case, said retainer ring having aninturned flange for holding a glass, a separator ring between the glassand the front wall of the case, said separator ring being convex wherebyits inner edge covers the edge portion of the dial, and an index pointermoved by said spring, said pointer being disposed between said glass anddial.

3. A thermometer comprising a cupped case having a front wall with ahole in it, a dial on the front wall of said case, a back closing theopen side of said case and fixed thereto, said back being of thinnermetal than said case, a heat sensitive spring and a pivot post withinsaid case, said pivot post having its front end in alinement with saidhole through the front face of said case, and a one-piece index pointerjournaled thereon, and projecting through said hole.

t. A casing for a thermometer comprising a shallow cup having a frontwall and an open side, the front wall of said cup having a dial madethereon, a back wall secured to said cup andclosing its open side, saidcup having an opening in its front and peripheral walls for theinsertion of an index pointer, and an outer ring closing the opening inthe peripheral wall of said cup.

5. A thermometer comprising a cupped case having an open side, a dial onthe front wall of said case, a back closing the open side of said caseand fixedto said case, a heat sensitive spring and a pivot post arrangedin the case, a pointer'rotatableon the end of said pivot post, saidpointer having an arm within said case pivoted on said post and adapted.for cooperation with said spring, said case having an opening in itsfront wall for said index pointer, said opening having a lateralextension in the peripheral Wall of the case ing the front Wall of saidcasing and having for said arm, and a ring covering said exan openingfor an index pointer, said bottension. tom having an enamel dial fusedon its 1:) a 6. A metal thermometer casing comprisouter side. 5 ing ashallow cup shape front portion hav- Signed at St. Louis, Missouri, this14th ing integral side walls and bottom, the day of February, 1916.bottom of said cup shape portion constitut- CHARLES D. BOLIN.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of I'atents, Washington, D. C.

